The Ullman et al U.S. Pat. No. 4,754,890 relates to a Tamper Evident Safety Seal such as one of the type used to seal the opening in a medicine bottle, the seal having a pull-tab formed by double folding a web of sealing material prior to punching a seal therefrom. Ullman et al U.S. Pat. No. 4,822,326 is directed to the method.
In prior art devices there are numerous examples of forming a fold on the edge of a longitudinal strip by folding the edge over with the aid of rollers. There are also devices known as "plows" which serve to roll an edge upward and over in order to form an edge on a material, as is illustrated in U.S. Pat. No. 3,012,603 Newsome et al. Also known in the prior art is a method of folding a material whereby the material is pulled into a straight die and gradually creased and folded in the die in a continuous manner whereby the folded material is pulled from the exit end of the die (see U.S. Pat. No. 4,582,743, relating to toilet paper).
In prior art devices, there has been a failure to accomplish one or more of the following objectives:
(1) Face wrinkles on the product must be eliminated.
(2) A smooth unwrinkled finish must be obtained.
(3) The fold and refold must be in the shape of a "z" with the total width and the folded outer edge being at the same point.
(4) The fold must be continuous with no interruptions.
(5) There should be no puckering or unevenness in the folded edge.
(6) The material must move through the apparatus with a minimum of effort and a minimum of pull.
(7) There must be no scratching or groove formation in the final surface of flat areas of the part in order to maintain appearance.
(8) The shaping apparatus must be constructed to have a minimum length.
(9) The apparatus must be able to fold both sides of the film when required, either by placing two sections of the device in series, or one section with folding operation on both sides of the material simultaneously.